In the prior art the main frame supports for the crimper rolls have been variously formed from cast constructions, bolted plates, and welded plates with the bores for the rotative support of the crimper rolls being initially rough bored prior to assembly and then finished bored after assembly of the plates. Since at least one of the crimper rolls is adjustably movable with respect to the other of the crimper rolls, the support for the movable crimper roll has to be mounted in such manner that the axes of both crimper rolls are aligned and parallel with each other at all positions of the movable crimper roll with respect to the other crimper roll. Sufficient space is often left in the design of the framework to enable an operator to manually position feeler gauges within the main framework of the stuffer box crimper in order to align and properly space the upper and lower scraper blades with respect to the upper and lower crimper rolls. As is well known to those skilled in the art, this type of adjustment requires a skilled operator, and the adjustment of one stuffer box crimper with respect to other stuffer box crimpers can vary with the consequence that there will be variability in tows passing through the various stuffer box crimpers. In other words, it is highly desirable that filter tows be uniform as possible from one stuffer box crimper to the next.
In some stuffer box crimper constructions, the crimper roll shafts and the locations where the shafts are supported for rotation are actually too remote from the crimper rolls. As a consequence, when a load is placed upon the upper crimper roll, for example, as from a diaphragm-actuated piston, the shafts for the upper and lower crimper rolls and the crimper rolls will deflect to such extent as to cause an undesirable change in the gap between the crimper rolls and the tips of the scraper blades. Filaments will become undesirably trapped in such gap, resulting in damaged tow, i.e., cut filaments, etc. It is, therefore, highly desirable that the supports for the crimper roll shafts be placed as close as possible to the crimper rolls to minimize any undesirable deflection.
It is also highly desirable that the stuffer box crimpers be easily replicated with the same tolerances, and that each such crimper be sufficiently rigid in construction to maintain such tolerances.
All such requirements as discussed above, as well as other requirements not discussed but known to those skilled in the art, serve to produce a more uniformly crimped product. Also as will be appreciated by those skilled in the art, all improvement in uniformity may not necessarily be evident in cigarette filter rod properties, for example, because the filter rod making processes may introduce some variation, even if the filter tow is perfectly uniform. This inherent process variation has been observed to increase with lower total denier filter tows.